From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9275643E9DF; Thu, 30 Jul 2026 15:10:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785424253; cv=none; b=Cz1yJTUUt7L0gt2YvC1wjFRyBtIR4kvxeFj5rZKr4+u7lXpvMCZ8QLLLRWq4DzgqWrhopf+AqDY26dwdImNWcEDrFTuGLn/TgQsTBDZ9xQHI67oFz3MXSFw7IA1kHjOuxOO+i16XD3+VUZQrScoBDt+ycAwurSJbg1yths8acwI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785424253; c=relaxed/simple; bh=Rk1ZRlqQ2nkcCVptDp4TQq3lfuECKvTYrW4J9OuG30k=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=EitpQPVvAP81pdSigrI9A+gdOO2Fvuq2VoXDFCMQMfPws1zy2Pt3InxyiKRTrdj6449xK/72u33zB1gqMsMS+39Dbcnm8OrzxbEHItZ1fIfB/4DMnNjna+vTe8kR2Fmlr1eZ/oLJpBGdcnDMKQDCYj8T8snMJqY7qsxLXM9HbOA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=ldDiMDlQ; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="ldDiMDlQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 03D751F00A3A; Thu, 30 Jul 2026 15:10:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1785424247; bh=7PJS9Yi+2QZXgtkJ1cSMnb6Bgvepe2nrouExPWp5qLY=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ldDiMDlQnXd+1pVviZSM+B5+hzgnlz3pwubzNn9TR3f85wNuKboysVV/DLNcKqbPR ARxYrY25DU0pcnIInM8ML1VSMyNWfHlahKuuURWSXXavV/3cWead/n4KzFB08FuN8w 09a8urzlMS1eh3k84GAEi6VVtRiRIRO8p8av4KEs= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Ashutosh Desai , Lyude Paul Subject: [PATCH 6.18 328/675] drm/dp/mst: fix OOB reads on 2-byte fields in sideband reply parsers Date: Thu, 30 Jul 2026 16:10:58 +0200 Message-ID: <20260730141452.098475683@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260730141445.110192266@linuxfoundation.org> References: <20260730141445.110192266@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ashutosh Desai commit 6b89ba3dba2f583626fb693e47e951ffb8bf591f upstream. Three sideband reply parsers read 16-bit fields as: val = (raw->msg[idx] << 8) | (raw->msg[idx+1]); and check bounds only after the fact. When idx == raw->curlen, raw->msg[idx+1] reads one byte past the received message data into the following struct fields (curchunk_len, curchunk_idx, curlen). Affected functions: - drm_dp_sideband_parse_enum_path_resources_ack() full_payload_bw_number and avail_payload_bw_number fields - drm_dp_sideband_parse_allocate_payload_ack() allocated_pbn field - drm_dp_sideband_parse_query_payload_ack() allocated_pbn field Fix by using a single combined check (idx + 2 > curlen) before each 2-byte read. Since the check is strictly tighter than idx > curlen, no separate step is needed. Fixes: ad7f8a1f9ced ("drm/helper: add Displayport multi-stream helper (v0.6)") Cc: # v3.17+ Signed-off-by: Ashutosh Desai Reviewed-by: Lyude Paul [added fixes tag] Signed-off-by: Lyude Paul Link: https://patch.msgid.link/20260510203128.2884846-1-ashutoshdesai993@gmail.com Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/display/drm_dp_mst_topology.c | 17 ++++------------- 1 file changed, 4 insertions(+), 13 deletions(-) --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c @@ -934,16 +934,13 @@ static bool drm_dp_sideband_parse_enum_p repmsg->u.path_resources.port_number = (raw->msg[idx] >> 4) & 0xf; repmsg->u.path_resources.fec_capable = raw->msg[idx] & 0x1; idx++; - if (idx > raw->curlen) + if (idx + 2 > raw->curlen) goto fail_len; repmsg->u.path_resources.full_payload_bw_number = (raw->msg[idx] << 8) | (raw->msg[idx+1]); idx += 2; - if (idx > raw->curlen) + if (idx + 2 > raw->curlen) goto fail_len; repmsg->u.path_resources.avail_payload_bw_number = (raw->msg[idx] << 8) | (raw->msg[idx+1]); - idx += 2; - if (idx > raw->curlen) - goto fail_len; return true; fail_len: DRM_DEBUG_KMS("enum resource parse length fail %d %d\n", idx, raw->curlen); @@ -961,12 +958,9 @@ static bool drm_dp_sideband_parse_alloca goto fail_len; repmsg->u.allocate_payload.vcpi = raw->msg[idx]; idx++; - if (idx > raw->curlen) + if (idx + 2 > raw->curlen) goto fail_len; repmsg->u.allocate_payload.allocated_pbn = (raw->msg[idx] << 8) | (raw->msg[idx+1]); - idx += 2; - if (idx > raw->curlen) - goto fail_len; return true; fail_len: DRM_DEBUG_KMS("allocate payload parse length fail %d %d\n", idx, raw->curlen); @@ -980,12 +974,9 @@ static bool drm_dp_sideband_parse_query_ repmsg->u.query_payload.port_number = (raw->msg[idx] >> 4) & 0xf; idx++; - if (idx > raw->curlen) + if (idx + 2 > raw->curlen) goto fail_len; repmsg->u.query_payload.allocated_pbn = (raw->msg[idx] << 8) | (raw->msg[idx + 1]); - idx += 2; - if (idx > raw->curlen) - goto fail_len; return true; fail_len: DRM_DEBUG_KMS("query payload parse length fail %d %d\n", idx, raw->curlen);